Spiral track centrifugal separator



Dec. 19, 1961 Z. VANE SPIRAL TRACK CENTRIFUGAL SEPARATOR 3 Sheets-Sheet1 Filed July 9, 1959 6%, WVE/WU/i Dec. 19, 1961 2. VANE 3,013,663

SPIRAL TRACK CENTRIFUGAL SEPARATOR Filed July 9, 1959 5 Sheets-Sheet 2WVE/VTUF Dec. 19, 1961 z. VANE 3,013,663

SPIRAL TRACK CENTRIFUGAL SEPARATOR Filed July 9, 1959 5 Sheets-Sheet 3United States Patent G 3,013,663 SPIRAL TRACK GENTRIFUGAL SEPARATORZdenek Vane, Box 225, Postal Station D, Ottawa, Ontario, Canada FiledJuly 9, 1959, Ser. No. 826,673 24 Claims. (61. 20-144) This inventionrelates to a method of and means for centrifugal separation of suspendedsolids in a fluid flow, and deals more specifically with separationsperformed in a continuous helical track. This application is acontinuation-in-part of my application Serial No. 470,496 filed November22, 1954, now abandoned.

Separations by centnifugal force, conducted in a free vortex, aresatisfactory wherever the handled material is fine enough to traversethe separator without choking the same. Separable materials however,with components which differ greatly in size and density as, forinstance, the grain product of a threshing machine, cannot be separatedeconomically in a free vortex type apparatus, if the carrier fluid flowis intercepted by the edges of separating members in axial direction andsaid edges project forward into the oncoming flow of the separablematerial. A constant risk of choking and plugging narrow passages,coupled in cyclones with a large pressure drop, exclude free-vortex typeseparators from a separation work of this kind.

1 have found that the advantages of centrifugal separation can beemployed for the above mentioned separable materials when, instead of afree vortex, a closed continuous spiral path is used for subjecting thetreated material to centrifugal tension, wherein narrow egress passagesfor the fine separated components have such a direction that they cannotbe choked by much coarser particles flowing past them, and a continuousseparation work is thus made possible. A spiral conduit with .a nearlystraight trajectory for the handled material, combined with separatingmembers having passages slanting backward from the main path for thetreated material, enable the use of centrifugal force for separations ofmaterials nonsuitable for a free vortex. The purpose of this inventionis to provide a method of multiple separations and a separator free fromchoking risks; the pressure drop is lower than that of a cyclone, butthe centrifugal tension therein developed can be compared to that of acyclone.

In general, it is an object of this invention to provide a method and anapparatus for multiple separations of components having disparate grainsizes and densities.

Another object of the invention is to provide a separator for grain sizeclassification and density separation with variable means of controllingthe grain size and density of components during the operation.

Still another objectis to provide a method of this kind with steps andmeans for keeping the separating members clean during the operation whenmaterials with a choking tendency and a sticky, clogging character aretreated.

In this invention, the flowing fluid is compelled to follow a helicalpath, defined by a closed continuous spiral track. At desirablelocations along the path, selected components of the fluid carrier maybe removed by the centrifugal tension developed in the fluid to driveportions thereof through apertures in the conduit .walls; for thispurpose, the conduit .has a helical direction and is provided with slotsto allow Stratified layers to be filtered ofi, roughly along a radiusfrom the helix axis. Slots in the outer conduit wall connect to acollecting conduit to separate heavy materials. Slots in the innerconduit wall provide an outlet for the lighter component to a conduitadjacent the helix axis. In order to compensate'for a pressure drop inthe main conduit'due to continuous ice losses through these collectingslots and to assist the separation of components into such collectingconduits, an additional fluid is fed into the circuit, across the mainconduit, through feed slots facing said collecting slots. The separatingoperation may be performed in the direction of the radius eitherinwardly, if it is desired to collect the lighter component, oroutwardly if the heavier component of the fluid is to be collected. Inthis second type, the slots in the inner wall of the main conduit arefeed slots and lead to a tfluid compensation supply, while the slots inthe outer wall lead to a collecting space. In the first type, the slotsin the outer wall of the helical conduit lead to a fluid compensationsupply, while those in the inner wall connect to a collecting space.Thus, in each case there is -a lateral flow of the additional fluidacross the main conduit, passing from feed slots to collecting slots.

In the drawings which illustrate embodiments invention FIGURE 1represents a partly cut-away elevation of the separator,

FIGURE 2 is a diagram explaining schematically the function of theseparating members of the apparatus in FIGURE 1,

FIGURE 3 shows variable means for control of the separator,

FIGURE 4 is a modification of the apparatus in FIG- URE 1,

FIGURE 5 is a diagram explaining the function of the apparatus in FIGURE4, and

FIGURE 6 represents a combination of both variation of the separator. 1

Generally, a system of three parallel conduits is so up in eachvariation of separator, wherein one of the conduits is the helical pathfor spinning a carrier fluid carrying a separable mixture, anotherconduit collects the separated components, and a third conduit suppliesan additional fluid flow of clean carrier to promote the of theseparation. The number of components separated is not limited, since thereceiving conduit may be divided lengthwise into any desired number ofsections, each section separating one selected component from thetreated mixture. The exchange of the carrier between the three conduitsand the egress of the separated components is conducted in the directionof the radius of the spin. The separation itself may proceed either in aradially inward or outward direction. Only one of the three conduitsmust have a spiral direction since it has to produce a centrifugaltension in the treated material. i

The separator, shown in FIGURE 1, separates radially inwardly; itconsists of a hollow standard 11, fixed in a base 12, and having a topoutlet opening 13, controllable by a bathe 14. This baflle is a valve ofany well known type, represented in the drawings by a's'ymbol only, andits purpose is to vary the cross-section area of the outlet 13, withoutclosing it completely. The standard 11 fHIlC- tions as a receivingconduit of the system;its' inner space 15, defined by a bottom 16, is acollecting space for the the standard wall 11' and the wall 19, isdivided by a vertical partition 20 into two parallel conduits, of whichthenumeral 21 designates the outer, and'thenumeralzz the inner conduit.1 Each of them is provided atthe'base 12 with a feed spout, numeral 23for the conduit 21, and numeral 24 for the conduit 22. Both conduits aresupplied with a suitable carrier fluid as air, either from one commonsource, or from two separate pressure sources, not shown in thedrawings. A separable mixture is fed into the carrier fluid flow in theconduit 22 by a hopper 25. The outer conduit, 21, has a progressivelydecreasing cross-section area, from the base to the top of theseparator; its purpose is to supply an additional carrier fluid neededto enhance the separation by a lateral, inwardly deflecting carrierflow, and this additional flow is dis continued at the point where theseparating members end. This point is marked by numeral 26, and showsthe end of the conduit 21 in dotted line. The outlet 27, provided with avolume control baflle 28, belongs to the conduit 22, the conduit 21being closed at the point 26. A separating area is provided in the wallof the standard 11, represented by series of openings 29, provided atthat part of the wall which is adjacent to the conduit 22; theseopenings 29 allow the egress of the separated components into thecollecting space 15. There are other series of openings numeral 30,similar to the first ones, provided in the vertical partition 20,radially adjacent to or a little ahead, in the direction of flow, of theseries of openings 29. Their purpose is to direct a flow of additionalcarrier fluid across the helical path of the conduit 22, thus actingagainst the centrifugal tension, to sweep away lighter components fromthe treated mixture through the egress openings 29 into the collectingspace 15. As the exact position of the respective series of openingscannot be clearly seen either from the elevation, or from a plan view, apart of the system of the three conduits is developed in FIGURE 2 in oneplane. The resulting diagram illustrates the separating area, which canbe partly seen in FIGURE 1: separating openings 29 have, when viewed inthe direction of flow shown by an arrow, clear backwardly slantingspacers 31 the angle of which, marked by A, formed with a tangent drawnto the inside periphery of the conduit 22, being a measure of protectionagainst choking said openings 29 by coarse material passing by. The flowthrough the separating openings 29 is controlled by the baflles 14 and28. The feed openings 30 have a forward slant. It will be noted that allconduits are sealed off from the outer space and from each, except thefeed inlets, separating passages and evacuating outlets shown in thedrawings.

In operation, the separable mixture fed from the hopper 25 into thecarrying fluid and passing through the conduit 22 is rotated on thehelical path thereof, and all particles heavier than the carrier aredriven by centrifugal tension outwardly to the wall defining saidconduit 22, i.e., to the partition 20. By proper controlling of the flowin the outlets 13 and 27, a radially directed inward flow of additionalcarrier fluid of any desired force is set up from the series of openings30 in the conduit 21 toward the series of openings 29 in the space ofthe hollow standard,

and sweeps from the outer periphery of the conduit 22 that part of thesuspended solid mixture which is specifically lighter and cannot resistsuch a lateral pressure. When a fine mixture of kernels and dirt,produced in a thresher for grain, is propelled by an air flow, all thefine dust and chafl particles are separated in this separation areathrough openings 29, and are collected in the space 15 to be evacuatedby the outlet 13. The remaining part of the mixture which is heavier andcomposed of kernels of good and medium quality and which resisted thelateral pressure of the additional air flow because of its greatermomentum, continues its travel along the conduit 22, to be evacuated bythe outlet 27. It is obvious that a clean carrier fluid only is fed intothe feed spout 23.

The angle A which the openings 29 form with the tangent tg drawn totheinner periphery of the helical path in the conduit 22, protects saidopenings against plugging. Said angle may be varied during the operationalong with the shape and the size of said openings, by a device shown inFIGURE 3a. Fine laminae 32 define egress openings 33 of the separatingmember 34; they are pivotally mounted, by means of fine suspensionjournals 35, in a larger passage cut out in the standard wall 11. Eachlamina is activated by another journal, numeral 36, to perform apivoting movement, the resulting new posit-ion being shown by dottedlines. All journals 36 of a separating member are joined by a narrowsteel belt 37, provided with slightly elongated holes 38, in whichjournals 36 may pivot in a short spiral movement. The belt 37 is thenconnected to a lever 39, activated outside of the standard 11. Thissystem of variable openings works in a similar way as the Venetianblind. In FIGURE 3b, another type of variable openings 40 is shown,wherein the included angle A is fixed, the size alone of the openingsbeing made variable. A fine steel belt 41 is punched so as to produceparallel holes, the punched material is bent on one side of the hole toform a directing vane 42 having a desired angle with the remaining partof the belt, and this belt is slidingly fastened on a series of similarholes provided in the standard 11, one side of which may also be bent toform another vane 42', so as to increase or reduce the passage formedthereby, when the belt is changed from position lengthwise. Obviously,the belt may be punched also by plain holes only, thus leaving thepassages without directing vanes 42, 42. The herein described system ofvariable openings, which assume a form of gratings similar to a concaveof a thresher, are able to replace advantageously an expensive andcomplex system of screens used normally in threshcrs. The protectionagainst choking of such gratings, and the possibility of changing thequality of the product during the operation by only varying the lateralflow through said gratings, without ofi periods, will be appreciatedespecially in thresher like machines wherein any change of the productquality requires normally an exchange of screens. It is obvious that theconduit 21 for the additional fluid need not have a helical direction,and may be given any other suitable form; the size of openings 29 mustbe large enough to intercept the selected components in their fullhelical speed. The bafiles 14 and 28 are to vary the crosssection areaof the respective outlets, said outlets never being closed completely,since no separation would then be possible.

In order to take advantage of all possibilities of quality control forseparated components, the additional fluid flow should be controlledalso in its pressure source before entering the spout 23. The size aloneof separating openings 29 is not decisive of the separating result,since the density of particles entering said openings will depend ratherfrom the angle A and from the lateral pressure exerted by the additionalfluid flow: the readiness of a par ticle to change its direction and toenter a slot 29 increases with the increasing angle A and with theincreasing force of the lateral pressure. When product density isconcerned, varying the passages for the fluid carrier in outlets 13 and27 has the same effect as if the size of the respective separatingopenings were varied. Varying the size alone of openings 29 willinfluence chiefly the size of separated particles if the other means ofcontrol remain unchanged. The smaller the angle and the sharper is thecurvature of the trajectory for a particle entering the slot; this meansa lower density of the separated particles and a smaller risk ofplugging the slot.

The apparatus shown in FIGURE 1 separates particles in a radially inwarddirection, thus acting against the centrifugal pressure, therebysubjecting the treated material to a severe density test. In FIGURE 4, amodification of said apparatus is shown wherein the separable particlesmove radially outward from the main flow, to be pcrmanently separated.The additional fluid flow enhancing the separation acts here in the sameway and direction as the centrifugal force does. This modified separatorconsists of a hollow standard 43 fixed in a base 44 and supporting theother structure parts. The upper end of the arated components is shownby smaller arrows.

standard 43 is closed by a cover 45; a sloped bottom 46 defines, alongwith the cover 45, the inside space 47 in the standard, as a conduit forthe additional fluid, introduced by a feed conduit 48. A closed spiraltrack is coiled on the standard 43, said track being formed by two flatspirals 49 and 50, joined by a vertical spiral partition 51, thusdefining a helical conduit 52, provided with a hopper 55, and the outlet54 with a volume controlling baffle 56. Parallel with the helicalconduit 52 is mounted a collecting conduit 57, defined by an outer wall58 and the two spirals '49, 50; this conduit 57 is to receive a flow ofcarrier fluid with therein suspended particles separated from thematerial traveling in the main helical conduit 52, and extends from theoutset point 59, near the bottom 46, to the end point 60, near the cover45. This collecting conduit 57 is thus shorter than the helical conduit52,

and is further divided lengthwise by a tight partition 60' in two parts,to collect two different separated components from the treated mixture;each part is then provided with an outlet pipe to drain the separatedproduct. The lower half of the conduit 57 is drained by the outlet 61,having a volume control baflie 61', and the upper half has an outletpipe 62 with a baffle 62'. The spiral partition 51 contains twogratings, each having a series of separating openings, the seriesnumeral 63 being for said lower part of conduit 57, and the seriesnumeral 64 for the upper part thereof. To each of these series ofopenings in the partition 51 corresponds, in the opposite wall ofconduit 52, a series of openings in the wall of the standard 43,slightly ahead in direction of flow, to discharge a lateral deflectingflow radially outward, thus increasing by its effect the centrifugalpressure of the spinning fluid and material on the partition 51. Saidseries of openings in standard 43 is marked by numeral 65 for the lowerpart, and by numeral 66 for the upper part of the conduit 57. Theseparating members containing the openings 63 and 64 are constructed forclassification according to grain size, as gratings of a sufiicientthickness to resist the wear by abrasion, resulting from a considerablefriction of the handled material against said members. The size ofopenings 64 is larger than that of the openings 63. All other detailsare the same as in FIGURE 1. The FIGURE is a diagram showing theposition of the separating members in the apparatus of FIGURE 4, whendeveloped in one plane.

In operation, a separable mixture is fed by the hopper 55 into the feedinlet 53 along with a flow of a carrier fluid entering said inlet from apressure source, not shown in the drawing. The mixture is rotated on thehelical path of the conduit 52, and is driven toward the spiralpartition 51 by centrifugal tension. All heavy and fine particles aretraveling along said partition 51, being pressed thereon by a layer ofcoarser and lighter components of the same mixture, traveling in thecentral part of the cross-section of conduit 52. The frictional contactwith the partition 51 reduces the velocity of the traveling fine partofthe mixture, thus increasing its readiness to enter a separatingopening in a radially outward direction. This readiness to change itstrajectory is further enhanced by the lateral flow of fluid coming fromopenings 65, when the treated mixture enters the Zone between the twoseries of openings 63 and 65. The position of the laminae in thegratings 63 is seen in FIGURE 5, the directionof the main flow beingmarked by a large arrow, while the trajectory of the sep- Such change ofdirection is made possible for the fine part of the mixture by a reducedspeed due to friction, and by a draft through said openings of thefluid, adjustable by a proper volume control in the outlet 61, by thebaffle 61. It is obvious that all structure parts participating in thisseparation must be tight enough, having no communication whatsoever withthe outside space, except by controllable outlets. Any desired speed andpressure then can be used. When a mixture produced by the cylinder of athresher, containing coarse straw, kernel bearing ears, chaff, kernelsand fine dust, is fed into the hopper 55, and a flow of air is propelledby conduits 48 and 52, the combined action of the centrifugal tensionand of the pressure caused by the additional air in a radially outwarddirection, will separate all fine dust, chaff and kernels in the firststage of separation, in the first separation area of this separator,defined by the openings of series 63 and 65, while the remaining mixtureof coarse straw and some kernel bearing ears which, due to their largersize, were unable to pass through the slots of the first separatingmember, continues its travel along the helical conduit 52, to meet thesecond separating area, series of openings 64 and 66, having openings oflarger size, wherein the heavier kernel bearing ears are separated fromthe coarse light straw in a similar way as the finer components in thefirst stage of separation. For these separations, the width of the slotsis about one inch for the first, and one inch and one half for thesecond stage of separation. As in the case of separator in FIGURE 1, thesize of separating openings alone does not determine the expectedresult,since the draft through said gratings is of prime importance. Theclean straw remaining from the second stage of separation is evacuatedby the outlet 54, while the kernel bearing ears are directed by theoutlet pipe 62 to the machine for re-threshing. The fine mixtureseparated according to grain size in the first stage of separation byopenings 63/ 65, will be object of a new separation according to densityin an apparatus shown in FIGURE 1, along with a fine part of grainseparated by the concave of the thresher itself. It is known that theconcave of a modern thresher separates up to percent of the fine grainfrom the coarse straw, so that this apparatus, FIGURE 4, has only asmall part thereof to separate. In standard threshers however, thissmall part, to be correctly separated, requires a very important andexpensive screen structure.

The two separator variations of FIGURES l and 4 are shown in FIGURE 6combined in one structure, wherein the centrifugal force performs, intwo successive steps, a complete separation work required in threshingoperations, with all advantages of the above single separators. Thislighterand space saving combination in FIGURE 6 is made possible byusing a helical wall 67 to divide the inner space of the hollow standard68 in two parallel conduits 69 and 70, one of which, numeral 69, isclosed by the bottom of standard and has an inlet 71, and functions asan additional fluid feed conduit for a separating coil 72 whichseparates radially outwardly; the other one, numeral 70, serves as acollecting conduit for a coil 73, separating radially inwardly. Thus,the coils 73 and 72 function in the same'way as the two separatorvariations described in FIGURES -l and 4 respectively, and FIGURE 6shows an elevation of the combined separator with the dividing wall 67in dotted lines. Said wall is formed by a helically twisted stripinserted and tighty fastened by its edges in the hollow standard 68 soas to seal off the two conduits 69 and 70 from each other. At the outsetpoint B the wall 67 forms a large conduit 69 which takes at this pointall the cross-section area of the inner space of standard 68; theconduit 70 starts at the same point B with a zero cross-section area, toincrease progressively its crosssection, thus reducing the conduit 69,until at the point '0 each of them occupies one' half of thecross-section area within the standard 68. This progressive changes goeson between the points C and D,'until at D the con,

in one plane, and would appear in an elongated rec- 'tangle of thestandard 68 as a diagonal.

The two auxiliary conduits 69 and 70 follow a helical path at the samepitch and direction as the two main coils 72 and. 73, and each of saidauxiliaries in standard 68 communi 3 cates with its respective mainconduit throughthecommon wall of the standard provided with slots of thesame kind as shown in FIGURES 1 and 2, numeral 29, and in FIGURES 4 and5, numeral 65. All the other parts of the structure in FIGURE 6 are alsoderived from the structures in FIGURES l to 5. The coil 72 is providedwith an inlet 76 and a hopper 77 to receive therethrough respectively aflow of air and a mixture of coarse straw, dirt, kernels and kernelbearing cars. This coil 72 classifies the materials according to grainsize, and has an outlet 78 at its top end, with a volume control valve79, to discharge the coarse straw, while the finer part of the mixtureis collected by a collecting conduit 80 adjacent the coil 72 fromoutside and divided by a vertical partition 81' in two parts, the lowerone being provided with an outlet spout 82 for kernels and fine dirt,while the upper half thereof is provided with an outlet spout 83 forkernel bearing ears. Both outlet spouts 82 and 83 have suitable variablevalves, not shown in the drawings, to control the flow of air passingtherethrough. The coil 72 has a common wall with the collecting conduit80, partition 84, which is slotted at suitable points, not shown in thedrawing, to allow the egress of the separated components. The slots areequivalent of those shown in FIGURES 4 and 5, numeral 63. The coil 73,equipped to separate materials radially inwardly according to density,in this case the fine dust and chafl from heavy kernels, is provided atthe base with an inlet 85 and a hopper 86 for introducing respectivelyan air flow and a mixture to be separated, and at the top with an outlet87 and a volume controlling valve 88. Adjacent thereto is an auxiliaryfeed conduit 89 with an inlet 90 to supply an additional air flowdirected from outside through suitable slots, not shown in the drawing,in the common wall, partition 91 between the two conduits 73 and 89;said slots are equivalent to those in FIGURES l and 2, numeral 39.Radially adjacent to such slots are located other slots in the wall ofstandard 68, corresponding to those in FIGURES l and 2, numeral 29, toreceive said additional air carrying light parts of the mixture andcoming across the main conduit of the coil 73 into the collectingspaceauxiliary conduit 70, wherefrom it is evacuated by outlet 74. Theheavy kernels which resisted, in this density test, the lateral pressureof the added air flow travel along the periphery of the coil 73, due tocentrifugal tension, and are evacuated at 87. The cross-section area ofthe auxiliary feed conduit 89 is decreasing progressively from the inlet90 to the end point 92.

In operation, the parts of this combined separator perform the samefunctions as in the above single apparatus: in the first stage, thecoarse output of a thresher is treated by the coil 72 between its points76 and 78; the spout 82 yields the fine dirt with good kernels, to betreated again in the coil 73, and the spout'83 yields kernel bearingears which are to be re-threshed. In the second stage, the coil 73handles, between its points 85 and 87, the finer part of the thresheroutput separated by the concave, along with that yielded by the outletspout 82, and evacuates the separated dirt by outlet 74, and the cleankernels by outlet 87.

It will be noted that the common walls, partitions 84 and 91, on whichthe treated mixture is pressed by centrifugal tension, may be given amore or less sloped position as in a tunnel, to keep the mixture evenlyspread on the screening surfaces. It depends on the flow velocity and onthe kind of the handled materials, what an angle this slope shall begiven. The vertical position of the partitions shown in the drawings isthat suitable for the highest velocities. The outer auxiliary conduits80 and 89 need not be helical. The dividing wall 67 need not behelically twisted either if the coils 72 and 73 make only a half a turn.

Any variation of the separator shown hereabove may be constructed forseparations of various materials. In many cases, the possibility ofvarying'and adjusting the size and density of the separated productduring the operation is an appreciable advantage. Some separablematerials show a tendency to clog on narrow passages, thus changing theseparating capacity of the separating members. Very small diflerences ofthis kind may be corrected in this apparatus by adjusting the flow ratein respective outlets, to keep the product quality constant. This way ofcorrecting the result may be combined with a change of size, shape andangle of the separating openings in the active members, as shown above.Finally, the clogging of materials may be avoided by adding, to theseparable material, particles of a suitable size and weight, whichproduce a scrubbing effect on the helical surfaces and the separatingmembers, thus removing constantly the therein clogging material andreintroducing it into the circuit. For instance, an apparatus of thistype, used in flour milling operations for screening the finely groundgrain kernels having a certain degree of humidity, necessary for acorrect comminuting, can be supplied with an air flow with the additionof small steel balls sweeping the passages constantly and keeping themclean; the balls, of course, are separated at the end of the trajectoryfor the screened material and re-introduced into the circuit by afeedback system.

I claim:

1. A method of centrifugal separation into fractions of suspendedseparable materials comprising the steps of: conveying a first fluidcarrier carrying separable materials in suspension along a helical pathin a first bounded space shaped in the form of a continous spiral, thussubjecting said materials in suspension to centrifugal force during aspin of said fluid carrier along said helical path, introducing anadditional fluid carrier into said first fluid carrier from a secondbounded space radially adjacent to said first space deflectedsubstantially in chordal directions of said spiral so as to shift, in achordal direction, a part of said first fluid carrier with a fraction ofsaid separable materials from said first space into a third boundedspace adjacent said first space radially opposite from said second spacewith respect to a longitudinal was of said spiral.

2. The method of claim 1 with the added step of introducing saidadditional fluid carrier into said first space at an acute angle, saidangle being included substantially within a downflow interval between atangent drawn to the periphery of the helical path on one side, and theradius at the point of tangency on the other side, and the step ofremoving said fraction of said separable materials in suspension withsaid part of said carrier fluid substantially at said acute angle intosaid third space, said acute angle being a means of controlling thedensity and the grain size of said separated fraction, and a measure ofprotection against blocking of passages by that part of said treatedmaterials in suspension which continue traveling along the helical pathin said first bounded space.

3. The method of claim 2 with the added step of varying thecross-sectional flow area of said additional fluid carrier so as to varythe volume of said separated fraction, and the density and the grainsize of the therein separated materials.

4. The method of claim 3 with the added step of varying said acute angleso as to control the density and the grain size of materials separatedin said fraction.

5. The method of claim 1 in which said additional fluid carrier isintroduced into said helical path in a radially inward'direction thusexerting a lateral deflecting pressure upon said first fluid carrieragainst said centrifugal force and shifting a fraction of lower densitymaterials from said first space into said third space, with the step ofcontrolling the flow rate of said additional fluid carrier to vary thedensity of said separated fraction by varying said lateral deflectingpressure exerted upon said materials in suspension.

6. The method of claim 1 in which said additional fluid carrier isintroduced into said first space substantially radially outwardly, thus,in the direction ofcentrifugal force and shifts a fraction of saidmaterials in suspension of smaller grain size and higher density fromsaid first space into said third space, with the step of controlling theflow rate of said additional fluid carrier to vary the volume of saidseparated fraction, and the density and the grain size of separatedmaterials.

7. The method of claim 1 with the added step of feeding said additionalfluid carrier in flows directed into said first space at an acute angle,said angle being included substantially within a downflow intervalbetween a tangent drawn to the periphery of the helical path on oneside. and the radius at the point of tangency on the other side, and thestep of removing separated fractions of said materials in suspensionwith a part of said fluid carrier from said first space in asubstantially radial direction in flows directed at said acute angle,said additional fluid carrier thus exerting a lateral deflectingpressure on said first fluid carrier across said helical path, saidacute angle being a means of controlling the density and the grain sizeof said separated fractions and a measure of protection against blockingof passages by that part of said treated materials in suspension whichcontinue traveling along the helical path in said first bounded space.

8. The method of claim 1 with the added step of conveying with saidsuspension, generally non-separable particles having a higher densitythan said separable materials, said higher density particles exerting ascrubbing effect on said helical path so as to sweep away andreintroduce into circulation any parts of said materials having cloggedto said path.

9. The method of claim 5 with the step of introducing said additionalfluid carrier at more than one point of the helical path into said firstfluid carrier and removing at each of such points a part of said fluidcarrier containing one fraction of said separated materials from saidhelical path, said lateral deflecting pressure exerted by saidadditional fluid carrier being graduated from one such point to theother of said helical path so as to remove fractions of treatedmaterials in partial flows the density of which increases from one pointof removal to the other.

10. The method of claim 9 in which said acute angle and cross-sectionareas of said flows are made variable so as to control the density offractions separated at any one of said points of removal.

' 11. The method of claim 6 with the step of introducing said additionalfluid carrier at more than one point of the helical path into said firstfluid carrier and removing at each of such points a part, of said fluidcarrier containing one fraction of said separated materials from saidhelical path, said lateral deflecting pressure exerted by saidadditional fluid carrier being graduated from one such point to theother of said helical path soas to remove fractions'of materials treatedin partial flows the density of which decreases and the grain size oftherein suspended particles increases from one point of removal to theother. 1

12. The method of claim 11 in which said angle and cross-section areasof said partial flows are made variable so as to control the density andthe grain size of particles of fractions separated at any one of saidpoints of removal.

13. A separator of the charatcer described comprising in combination: aclosed helical walled main conduit having a center and a longitudinalaxis of a helix, said axis being located outside said main conduit, saidmain conduit having an inlet and an outlet portion, and having twointersections of said main conduit with any one radius of said helixnormal to said axis and passing through the center of said main conduit,the two intersections being located in two portions of the wall of saidmain conduit which are substantially opposite to each other in said thatthe shape of said openings and said acute variable.

10 main conduit, aseries of feed apertures in said main conduit in aportion of the wall thereof which is substantially adjacent to one ofthe two intersections of said main conduit with said radius of saidhelix, a series of egress slots in said main conduit in a portion of thewall thereof adjacent to the other of said'intersections andsubstantially radially opposite to said series of said feed apertures,said series of feed apertures being thus substantially radially alignedto said series of said egress slots in said main conduit, a closedauxiliary feed conduit radially adjacent to said main conduit andextending from a point of said main conduit where said series of feedapertures begins to that point of said main conduit where said series offeed apertures ends, a closed auxiliary collecting conduit radiallyadjacent said main conduit but substantially radially opposite to saidauxiliary feed conduit and extending from a point of said main conduitwhere said series of said egress slots begins to'that point of said mainconduit where said series of said egress slots ends, means connecting afluid carrier supply source to said auxiliary feed conduit and to saidinlet portion of said main conduit, means to supply materials to betreated into said fluid carrier in said main conduit, and a fluidcarrier outlet connected to said auxiliary collecting con duit.

14. The separator of claim 13 wherein said egress slots are defined bydirecting vanes and include an acute angle with a tangent drawn to thehelix of the main conduit,

said helix being defined by any one of said portions of said wall inwhich said slots may be located, said angle being included within adownflow interval between said tangent on one side andthe radius at thepoint of tangency on the other side, said vanes thus having a clearbackward slope in the helical direction of the main conduit so thatedges of said vanes adjacent said main conduit cannot accroach coarsematerials traveling down said main conduit.

15. The sepanator of claim 14 wherein said feed apertures areprovidedwith similar directing vanes as said egress slots at a susbtantiallysimilar angle to the direction of saidmain conduit and arranged insymmetry with said egress-slots vanes.

16. The separator of claim 13 wherein each of said slots and apertureshas a variable cross-section area, said area being defined by thecorrespondence between a fixed opening in the main conduit wall and anopening in a steel belt adapted to slidingly overlie the fixed openlugs.

17. The separator of claim 15 wherein said directing vanes are pivotallymounted on journals lodged in the walls of said main conduit, said vanesbeing further provided with journals fixed to said vanes and joined witha belt to operate a pivotal movement of said vanes so angle are 18. Theseparator of claim 13 having more than one series of egress slotsarranged in spaced relation to each other along said main conduit andhaving an auxiliary collecting means divided lengthwise i'ntoportionssealed from each other so that each of said series of egress slots hasits own collecting means provided with-amoutlet for one separatedfraction, said main conduit being provided with more than one series offeed apertures so that each of said series of egress slots is faced,across said main conduit, with a series of feed apertures substantiallyra-' dially opposite thereto, said series of feed apertures having acommon closed auxiliary feed conduit, said feed conduit having one endthereof connected to a fluid carrier supply source while said feedconduit is closed at the other end, said series of egress slots beingarranged so that said slots are increasing in size from one series tothe other. i

19. The separator of claim 18 having two series of egress slots in aspaced relation along the inside periphery of said main conduit andauxiliary collecting means in the form of a hollow standard, saidstandard supporting the separator structure and enclosing the helicalaxis of the main conduit, said main conduit being coiled around saidstandard, each one of the two series of said egress slots discharginginto one portion of said collecting means defined by said standard, eachof said sections being further provided with an outlet and with a flowrate control for one separated fraction, an auxiliary feed conduitradially adjacent said main conduit on the outer periphery thereof andhaving two series of feed apertures connecting said feed conduit withsaid main conduit, one series of said apertures being located slightlyahead of said first series of egress slots, the second series of saidapertures located slightly ahead of said second series of egress slots.

20. The separator of claim 18 having two series of egress slots inspaced relation on the outside periphery of said main conduit andauxiliary feed means in the form of a hollow standard, said standardsupporting the separator structure and enclosing the helical axis of themain conduit, said main conduit being coiled around said standard, eachone of said series of egress slots discharging into one section of saidcollecting means located substantially radially adjacent to the outerperiphery of said main conduit, each of said collecting-means sectionsbeing further provided with an outlet and a flow rate control means forone separated fraction, and auxiliary feed means defined by saidstandard, said hollow standard being closed at its bottom and at itstop, said standard having an inlet connected to a fluid carrier supplysource and two series of feed apertures in a wall common with said mainconduit.

21. A separator of claim 13 having said series of egress slots shaped asgratings constituted by fixed slots punched in the wall of saidcollecting conduit with a steel belt having similar slots to slidinglyoverlie said fixed slots in the main conduit wall, said fixed slotshaving one side of punched material bent to form a directing vane on oneside of said fixed slot, while said belt contains slots with punchedmaterial bent on the other side of said slots so that each completedslot has two directing vanes at a fixed tangential angle and enablingsaid slot to have a variable cross-section.

22. The separator of claim 21 with slots having only one side providedwith directing vanes.

23. The separator of claim 21 with slots constituted by plain holesonly.

24. A centrifugal separator of the character described comprising: ahollow standard supporting two helicalwalled main conduits coiled aroundsaid standard, said standard enclosing a helix axis for the two mainconduits, each of said main conduits having that part of their wallswhich is nearest to said axis common with said standard, said standarddefining an inner space which is divided lengthwise in the part thereofadjacent to said common walls into two parallel inner conduits by ametal strip sealing ofi said two inner conduits from each other in sucha manner that the first of said inner conduits extends over the entirecross-section area of said inner space at the direction of the helicalaxis to the profit of the second inner conduit, but decreasesprogressively said area in the direction of the helical axis the profitof the second inner conduit until said second inner conduit extends overthe whole cross-section area of said inner space while said first innerconduit ends by zero cross-section area at the end point of said commonwalls, said first inner conduit being provided with an inlet and meansfor connecting to an additional fiuid carrier supply source at thatpoint where said first inner conduit occupies the whole area of saidinner space and where said second inner conduit begins; a series of feedapertures in the common wall between the first of said main conduits andsaid first inner conduit, said series of feed apertures extending alongthe whole length of said common wall of said first inner conduit withsaid first main conduit; a series of egress slots in said common wallbetween said second main conduit and said second inner conduit, saidsecond inner conduit being provided with an outlet for one separatedfraction of materials treated; an outer collecting means radiallyadjacent said first main conduit and radially opposite to said firstinner conduit, said outer collecting means being divided in two sectionsto collect two different fractions of materials treated, a first seriesof smaller egress slots connecting said first main conduit with thefirst of the two sections of said outer collectiug means to collect afirst fraction of separated materials of relatively small grain size,said first series of egress slots being substantially radially alignedwith the first half of said series of said feed apertures in said firstmain conduit; a second series of larger egress slots connecting saidfirst main conduit with the second section of said outer collectingmeans to collect a second fraction of separated materials of largersize, said second series of larger egress slots being substantiallyradially aligned with the second half of said feed apertures in saidfirst main conduit, each of said two sections of said outer collectingmeans being further provided with an outlet for one separated fractionof materials treated; an outer and radially opposite to said secondinner conduit, said outer feed means extending from the outset point ofsaid common wall to the end thereof, a series of feed aperturesconnecting said outer feed means with said second main conduit, saidseries of feed apertures in said second main conduit being substantiallyradially aligned with said series of egress slots connecting said secondmain conduit with said second inner conduit; means to feed a fluidcarrier into said second main conduit and means to feed into said fluidcarrier in said second main conduit other materials to be treated; aninlet in said outer feed means and means connecting said inlet in saidouter feed means with an additional fluid carrier supply source, andtight closing means on the end point of said outer feed means.

References Cited in the file of this patent UNITED STATES PATENTS1,023,750 Morscher Apr. 16, l9l2 1,666,476 Stebbins Apr. 17, 19281,675,941 Lindsay July 3, 1928 1,861,247 Stebbins May 31, 1932 2,709,397Banning May 31, 1955 2,762,610 Puhe-Westerheide Sept. 11, 1956 2,829,771Dahlstrom Apr. 8,1958

